1. Field of the Invention
This invention relates to controlling body fluid condition using diuretics.
2. Description of the Related Art
Body fluid imbalance is associated with many diseases such as congestive heart failure, liver cirrhosis and kidney disease. Congestive heart failure in particular is a major cause of death and hospitalization. Despite currently available treatment, mortality and hospitalization from congestive heart failure remains high. Causes of heart failure include coronary artery disease, hypertension, valvular heart disease, myocardial infarction, etc. As pump function of the heart deteriorates, body fluid often increases and may lead to complications such as pulmonary edema.
When pumping capacity of the heart deteriorates, blood perfusion to the kidneys decreases. This results in retention and accumulation of body fluid because excessive body fluid is not delivered to the kidneys to be excreted. This excessive body fluid often manifests as swelling of the legs. If body fluid continues to expand, a weak heart may be no longer able to handle increased blood volume and finally fails to pump blood forward adequately. Symptoms of congestive heart failure include shortness of breath, fatigue, swelling of legs, orthopnea, paroxysmal nocturnal dyspnea (not being able to breathe suddenly at night). Many people come to the emergency room due to congestive heart failure exacerbation. People do not breathe well when fluid builds up in the lungs.
Diuretics such as hydrochlorothiazide, furosemide and bumetanide are often used to treat this fluid accumulation by increasing the excretion of body fluid and sodium through the kidneys. However, use of oral diuretics often fails to prevent heart failure exacerbation. This failure of diuretics to prevent heart failure can be explained by several mechanisms. First, the dosage of oral diuretics prescribed by the doctor is often fixed, but the ideal dosage often changes depending on changing body conditions. For example, when people with heart disease eat salty food high in sodium content, their body fluid may increase significantly. We often see people come to the emergency room after they eat excessive amount of salt at a party. In this situation, people will require a higher dose of diuretics in order to excrete excessive body fluid and salt. The required dose of diuretics is affected by the dietary intake of sodium, water and tendency to retain sodium. When body fluid builds up in the digestive system, it may cause intestinal edema (swelling). Bioavailability of diuretics may decrease with intestinal swelling. The body may not be able to absorb diuretics effectively. Patients may need to take higher dose of diuretics when poor bioavailability occurs.
Second, poor compliance plays a role. People sometimes forget to take medications. This poor compliance could result in heart failure. Third, treatment delay plays a role. When there is a sign of body fluid accumulation such as swelling of legs, many people ignore this early sign of heart failure and wait until their condition gets severe enough to require hospitalization. These explanations are associated with many cases of heart failure.
Sliding scale diuretic titration of oral diuretics has been attempted for the treatment of congestive heart failure by some heart failure management programs. In sliding scale diuretic titration, patients are instructed to measure body weights and adjust diuretics pill dose according to the instruction given by their physician or nurse. However, conventional diuretic sliding scale titration has several significant drawbacks. First, patients may not understand the sliding scale instruction or may not comply with it. Poor understanding of the instruction may also lead to inappropriate use of medication. Second, conventional instructions may be limited to instructions and sliding scale titration that are simpler than would be desired. In real clinical situations, a more complex diuretic titration may be required to maintain ideal body fluid condition. However, some patients may not be able to follow such complex instructions so instructions may be simplified at the cost of a less effective titration.
In addition, if the sliding scale diuretic titration changes frequently, some patients may not understand the change of sliding scale diuretic titration and may end up taking the wrong dose of medication. This may lead to serious complications. Taking too much medication may lead to complications such as dehydration, electrolyte imbalance, hypotension, and kidney failure. Conventional sliding scale diuretic titration is also limited to oral diuretics, which may not be as effective as, for example, continuous infusion of diuretics.
As a result of these possible complications, sliding scale diuretic titration, when attempted, is typically based on a straightforward and simple protocol. More complex protocols generally have not been attempted because there is not a reliable way to carefully monitor and control the dispensing of diuretic or to adjust the dose according to varying conditions. In addition, there are not reliable safety measures to safeguard against the possible inappropriate use of diuretics. Without such controls and safety measures, more complex protocols can have a higher risk of inappropriate use of diuretics and possible adverse effects such as dehydration, electrolytes abnormalities, hypotension, and kidney failure.
Thus, there is a need for better, and preferably automatic, approaches to control body fluid condition using diuretics.